Dexmedetomidine combined with local anesthetics in thoracic paravertebral block A systematic review and meta-analysis of randomized controlled trials

Background Dexmedetomidine (DEX) improves postoperative pain scores and prolongs the duration of blockage when combined with local anesthetics (LAs) for neuraxial and brachial plexus block; however, there is little information about the effectiveness of DEX as an adjuvant to LAs in paravertebral block (PVB). Therefore, a systematic review and meta-analysis were performed to evaluate the safety and efficacy of DEX combined with LAs in PVB. Method An electronic database search from inception date to February 2018 was performed. Randomized controlled trials (RCTs) comparing DEX as an adjuvant to LAs with LAs alone for PVB in adult patients were included. Postoperative pain scores, duration of analgesia, cumulative perioperative analgesic consumption, and adverse events were analyzed. Result We identified 7 trials enrolling 350 patients and found that DEX reduced pain scores at rest by standardized mean differences (SMD) -0.86cm (95% confidence interval [CI] [-1.55, -0.17], P = .01) and SMD -0.93cm (95% CI [-1.41, -0.26], P=.008) at postoperative 12hours and 24hours, respectively. DEX reduced pain scores while dynamic by SMD -1.63cm (95% CI [-2.92, -0.34], P=.01) and SMD -1.78cm (95% CI [-2.66, -0.90], P=.007) for postoperative 12hours and 24hours, respectively. DEX extended the duration of analgesia by weighted mean differences (WMD) 201.53 minutes (95% CI [33.45, 369.61], P=.02); and reduced cumulative postoperative analgesic consumption by WMD -7.71mg (95% CI [-10.64, -4.78], P<.001) andWMD -45.64 mg (95% CI [-69.76, -21.53], P<.001) for 24 hours morphine and 48hours tramadol subgroups, respectively. DEX also increased the odds of hypotension by odds ratio (OR) 4.40 (95% CI [1.37, 14.17], P=.01); however, there was no statistically significant difference for intraoperative fentanyl consumption and the incidence of the bradycardia. Conclusions DEX combined with LAs in PVB significantly improved postoperative pain scores, prolonged the duration of analgesia, reduced postoperative analgesic consumption, and increased the odds of hypotension. However, we cannot neglect the heterogeneity of the included RCTs. More large-scale prospective studies are needed to further clarify the above conclusions.